Collapsible tap.



" PATENTED AUG. 25, 1908.

Mm W 2 w 9 m. H M 8 8 VI/H'NESSES UNITED sTATns PATENT onnron.

ANDREW GRANSTROM, OF READVILLE, MASSACHUSETTS.

COLLAPSIBLE TAP.

Application filed April 29, 1907.

To all whom it may concern:

Be it known that I, ANDREW GRANSTROM, of Readville, in the county ofNorfolk and State of Massachusetts, have invented certain new and usefulImprovements in Collapsible Taps, of which the following is aspecification.

This invention relates to collapsible taps.

More particularly, it relates to means for causing the teeth of a tap tobe withdrawn out of engagement with the thread which they are cutting,so that the tap can be re moved in a straight axial direction withoutunscrewing it from the thread.

The object of the invention is to provide improved means for withdrawingthe teeth and resetting them, and to efiect the other improvements inapparatus of this sort which are found in the device hereinafterdescribed.

One embodiment of the invention is shown in the accompanying drawings,in which Figure 1 represents, in elevation, a collapsible tap, the partsbeing set for cutting. Fig. 2 represents the same in section, with theparts collapsed. Fig. 3 is a plan in section on the line 33 of Fig. 1.Fig. 4 is a plan in section on the line 44 of Fig. 2.

Referring to the drawings: 10 represents the stationary head of amachine in which the tap is to be set, and 11 is a stationary ring, theuse of. which is hereinafter ex plained, attached to the head by arms12.

13 is the rotating spindle of the machine, having. a chuck end forreceiving the shank 14 of the tap in the ordinary or in any suit-,

able manner.

The body of the tap is designated 15 and is here represented tapering asa pipe tap. It has blades 16 carrying the cutting teeth, which areslidably mounted in grooves 17 in the body of the tap. These groovespitch inwardly toward the axis, and downwardly with a suitableinclination, so that when the blades are slid downward with respect tothe body they are drawn inward toward the axis. This is accomplished byproviding the groove with an under-cut rabbet 18, and by providing theblade with a flange which fits into the rabbet, so that the blade isdove-tailed into the groove. The upper ends of the blades have lugs 19projecting radially and engaging in an internal annular groove 20 in aring 21 which surrounds the body of the tap. By movement of the ring upor down the blades are pulled up or down in their grooves and are thusexpanded to their working position, as

Specification of Letters Patent.

Patented Aug. 25, 1908.

Serial No. 370,753.

shown in Fig. 1, or are collapsed into position for withdrawal from thework, which is the position represented in Fig. 2.

The automatic collapse and resetting of the blades is effected asfollows: A rin 22 surrounds the body and blades, and has pins 23projecting upward from it loosely through ring 21. The upper end of eachpin is pivotally attached at 24 to a lever 25 which passes through aslot 26 in the body of the tap above ring 21. These levers are fulcrumedon a pin 27 set centrally in the body, and bear downward on the ring 21on the other side of the body from the place where they are attachedrespectively to their pins 23. Upon raising ring 22 with respect to thebody of the tap, pins 23'are carried upward, each of which raises oneend. of its lever 25, depressing the opposite end 28 of such lever, thusdepressing ring 21 with respect to the body. This moves the blades 16downward, and the grooves in which they move carry them inward, outofthe threads which they are cutting. This operation is automaticallyeffected when the tap has entered its work far enough for ring 22 toencounter the top of the work. When this happens the blades are throwninward and the tap may be withdrawn in a direct line axially by raisingthe spindle 13 in the ordinary manner, until the tops of the pins 23encounter the fixed ring 11 whichpushes them downward, returning ring 22downward with respect to the tap body and raising the lever ends 28,thus raising ring 21 (with which these lever ends are in engagement bymeans of slots in side straps 34) and raising blades 16 which arecarried outward to their active positions by the incline of theirgrooves. The tap is then ready for fresh work.

It is desirable to arrange the leverage about the fulcrum 25 so that theattachment to pins 23 is at a shorter distance than the bearing downwardupon ring 21, so that said ring 21 will be thrown downward faster thanthe blades are traveling with the general feed of the tap, and will bethrown out of their threads in the radial direction rapidly enough. Theamount of this difference of leverage depends in part upon the angle atwhich the grooves 17 are cut. The attachments 24 to pins 23 may be madeat any desired point, and for this purpose binding screws arerepresented in the drawings, although any other suitable form ofattachment might be employed. A stop 30 set in ring 21 limits thedownward motion of that ring by impinging against the body at the bottomof slot 26; and other stops 31 limit the upward movement of blades 16. Afriction plug 33 may be provided to maintain the parts normally inwhatever position they are driven by the above described action of themechanism.

While the 'foregoing illustrates one form in which the invention may beapplied, the invention is not limited to that, but may be embodied invarious forms without departing 'from its scope.

I claim:

1. A collapsible tap comprising a body portion; blades movable in acombined longitudinal and radial direction thereon, collapsing radiallyas they move endward longitudinally; a lever having one arm actuatingsaid blades, 'fulcrumed on the body and having its other arm adapted tobe operated by a stationary external body when the tap -feeds forward;the arm from the blades to the lulcrum being longer than from thefulcrum to the point of application on the lever of the force resultingfrom such external engagement.

2. A collapsible tap, comprising a body portion; blades movable in acombined longitudinal and radial direction on the body portion,collapsing radially as they advance longitudinally; a lever mounted andfulcrumed on. the body; said lever being arranged transversely of thebody, on one side operatively connected. with the blades and 011 theother side being adapted to be operated by one or more externalstationary bodies.

3. A collapsible tap, comprising a body portion; having grooves inclinedto its axis and blades slidable therein; in combination with lugs on theblades; a member mounted on the body and movable thereon parallel to itsaxis, in engagement with said lugs; a lever fulcrumed and supported onthe body, having one arm engaging said member and the other armpositioned to receive impulse for actuating the lever.

4. A collapsible tap, comprising a body portion having grooves inclinedto the axis, blades slidable therein, a movable ring sur rounding thebody and engaging the blades, another movable ring surrounding the bodyand adapted to engage the work; in combination with levers fulcrumed onthe body and engaging the two rings.

In testimony whereof I hereto affix my signature, in presence of twowitnesses.

ANDREW GRANSTROMv l/Vitnesses EVERETT E. KENT, M. E. MURPHY.

